The present invention relates to systems employing microprocessors, and particularly to integrated circuit elements which help to manage the operation of a microprocessor and/or of a system including a microprocessor. The field of personal computers has expanded upward to include many models and types of computers, with capabilities far beyond those of the earlier high-volume models (such as the IBM PC or the Apple Macintosh). Processor width and speed have increased, bus speed has increased, memory space has increased, and mass storage volume has increased.
However, in some respects such systems have not advanced at all. The most advanced 80386- or 68030-based systems are still turned on and off with a simple manual switch. This is related to a general limitation of conventional microcomputer system architectures: power-up and power-down are still, to a large extent, treated as if they were catastrophic events which are not within the purview of the system designer. The power-up operation of an 80486 system in 1989 is still quite similar to that of a Z80 or 8080 system in 1979. The system handling of these events has not kept pace with the general evolution of microcomputer user interfaces over the 1970s and 1980s. For example, one very frequent problem is accidentally kicking the plug of a microcomputer system, which suddenly removes power from the system and destroys work in progress.
Portable and laptop computers (especially battery-powered units) may include a time-out mechanism which shuts off power to the screen, if no keystrokes are entered for a period of time, until the user again enters a keystroke. However, this type of operation typically does not shut off power to the main processor.
A further significant limitation, from the system designer's point of view, is the necessity to have a large power switch readily accessible. Much effort has been put into designing external housings for computers which permit ready access to all needed functions, and space for all needed connections, and minimum desktop footprint, and convenient monitor size and visibility. Obviously some conflict exists among these criteria, and many industrial designers would be very happy to avoid the need for the power switch to be readily accessible. In many current designs, the power switch is located on the back of the case, where it is not very readily accessible. This is inconvenient for many users. However, in conventional architectures, the power switch must not be too accessible, lest it be accidentally bumped with disastrous results.
A further line of development has been the introduction of battery-powered systems. Advances in display and disk drive technology have greatly increased the functionality which can be included in such a system. Such systems are rapidly gaining in popularity, and offer the potential for many new system applications. However, in most such systems, battery lifetime is always a critical consideration, and any steps which can be taken to reduce power consumption will be very useful. Any reduction in power consumption can be used to provide longer lifetime, more functionality, lighter weight, or lower cost.
Much engineering has been devoted to automatic turn-off and power-saving features in calculators. See, for example, U.S. Pat. Nos. 4,409,665 and 4,317,181, which are hereby incorporated by reference. However, these are much simpler than a full microcomputer system, and do not nearly present the same system issues.
The present invention provides a significant advance in system configuration. In systems according to the present invention, a power-switching device (such as a gate-controlled triac) is used to connect and disconnect a computer system's power supply unit from the power-line connection. This power-switching device is controlled by a battery-powered circuit. The battery-powered circuit monitors a contact, and powers up the system when the user touches the contact. Thus, when the system is powered down, all parts of the system are disconnected from AC power.
In the presently preferred embodiment, this is accomplished by an auxiliary integrated circuit which monitors the contact pad, and causes the rest of the system to be powered up if the user contacts the contact pad. The auxiliary chip of the presently preferred embodiment performs other functions as well, which provide notable system advantages.
In the preferred embodiment, the contact pad can be used at any time to turn the system on or off. The battery-backed circuitry for this control input is configured so that drain on the battery is minimized, and the battery will have a long lifetime (in excess of 10 years) in normal operation.
The contact pad, in the preferred embodiment, is connected to a grounded capacitor, and is normally pulled up by a very weak P-channel pull-up transistor. (In the presently preferred embodiment, this transistor has nominal width/length dimensions of 5/20 microns (in a design where the minimum geometry is 2 microns), and therefore provides a maximum current of only about 10 .mu.A at 3 Volts V.sub.BAT supply.) When the user contacts this pad (and discharges the capacitor), the resulting falling edge docks a flip-flop, and the output of this flip-flop is connected (through an optical isolation stage) to activate the power supply. To avoid battery drain (e.g. if the user accidentally leaves an object in contact with the contact pad while the system is unplugged from the wall socket), a timing circuit is included, which will turn off current to the optical isolator if the system has not powered up within 100-200 msec after the user touches the contact pad.
Of course, a wide variety of switches can be used, in alternative system configurations, to generate the falling edge at the contact pad, and the advantages of the disclosed system architecture can still be obtained.
System designers may choose to locate the contact in a variety of convenient locations. The contact may be located close to the monitor, or close to the keyboard, or remote from the rest of the system (e.g. as a wall panel). The contact may be made very large if desired (e.g. to cover a significant fraction of the external area of the monitor, or of the system box), especially if the system is configured so that the large contact only causes system turn-on, and not turn-off, or if the system includes some software protection against accidental turn-off.
A significant advantage of this system is that the advantages of electronic power switching are obtained,, but routing of the line voltage is very restricted. That is, the only parts of the system which are exposed to the full line voltage are the power supply itself, the switching triac, and the opto-isolator. Thus, system design and reconfiguration is simplified, since the vast majority of the electronic components are never exposed to full line voltage.
A separate line of technological progress is the increasing use of batteries, in integrated circuit packages or in very small modules, to provide nonvolatile data retention. Here the driving concern is not the system power budget, but reliability and robustness. The availability of battery backup can be used to ensure that power outages or power-line noise cannot cause loss of data (including configuration data). For example, modern semiconductor technology has provided solid-state memories with such low standby power requirements that a single coin-sized battery can power the memory for ten years of lifetime or more. Such memories are already commercially available.
Low-power microcontrollers have also been commercially available in recent years. An unusual example of such a microcontroller is the DS5000 Soft MicroController.TM.. (This integrated circuit and its data sheet are available from Dallas Semiconductor Corporation, 4350 Beltwood Parkway, Dallas, Tex. 75244, and are both hereby incorporated by reference.) The DS5000 is a microcontroller which has a small battery packaged with it, to provide nonvolatility. Microprocessors and microcontrollers of this kind are extremely useful, since the internal memory of the microprocessor is always preserved. Therefore, the microprocessor can be programmed to "learn" while in service, or to internally store a parameter set which is adjustable throughout the lifetime of the microprocessor. However, aside from their nonvolatility, such microprocessors are typically not the highest-performing microprocessors. Thus, a user who needs nonvolatility may need to make some difficult choices.
The present invention provides an auxiliary integrated circuit, which can interface with a microprocessor (or other complex random logic chip) in a way which improves the microprocessor's power management during power-up and power-down transitions.
The embodiments disclosed in the parent applications provided an auxiliary chip which can provide all necessary functions for power supply monitoring, reset control, and memory back-up in microprocessor based systems. The present application discloses an improved preferred embodiment, which has been enhanced by capability for the touch-initiated "kickstart" function described above.
The systems provided by the disclosed innovative teachings provide all the advantages of software-controlled power-up, while maintaining excellent safety (and regulatory compliance). The systems provided by the disclosed innovative teachings also provide all the advantages of software-controlled power-up, while maintaining good immunity to glitch-induced erroneous system turn-on. The disclosed innovative systems, using an auxiliary chip as described, can provide substantial advantages over conventional systems in some or all of the following areas:
User convenience PA0 System package design PA0 Reliability PA0 Power conservation PA0 Safety (due to use of low voltage)